OsNramp5基因功能缺失型镉低积累水稻旱育秧赤枯病的发生与防治OA

Breeding low-cadmium(Cd)rice varieties is an economical and effective approach to address the problem of excessive Cd levels in rice grains.Low-Cd Zhenliangyou 8612,a hybrid rice combination with loss-of-function OsNramp5,has been developed by heavy-ion beam mutagenesis combined with M1 generation targeted deep sequencing(M1TDS)technology.This variety exhibited good yield potential and stable low Cd accumulation characteristic in multi-site trials,demonstrations,and promotions in the middle and lower reaches of the Yangtze River.However,during the demonstration planting process in Deyang of Sichuan Province,located in the upper reaches of the Yangtze River,dry-raised seedlings of low-Cd Zhenliangyou 8612 developed akagare disease symptoms,characterized by interveinal chlorosis and brown needle-like spots on the leaves,which closely resembled typical manganese(Mn)deficiency symptoms.To further confirm the cause of these akagare disease symptoms and propose control measures,this study compared the responses to low Mn conditions between the control Zhenliangyou 8612 and low-Cd rice varieties(low-Cd Zhenliangyou 8612 and low-Cd Zhenliangyou 3061)by hydroponic culture at the seedling stage.The results showed that at a low Mn concentration(0.08 µmol/L),both low-Cd rice varieties exhibited phenotypes highly similar to akagare disease symptoms described above.Compared with Zhenliangyou 8612,low-Cd Zhenliangyou 8612 showed significant decreases of 33.38％,25.38％,56.75％,and 65.18％in the plant height,root length,above-ground dry weight,and below-ground dry weight,respectively.The corresponding significant reductions in low-Cd Zhenliangyou 3061 were 30.12％,24.25％,56.13％,and 63.45％,respectively.Under hydroponic culture conditions with a low Mn concentration(0.08 µmol/L),foliar application of Mn fertilizer at 30 000 μmol/L significantly alleviated akagare disease symptoms in low-Cd rice varieties and partially restored the plant height,root length,and above-ground and below-ground dry weights compared with the treatment without foliar application of Mn fertilizer.For dry-raised seedlings,foliar application of Mn fertilizer at 30 000 μmol/L 14 days after sowing markedly reduced akagare disease symptoms in low-Cd rice varieties,recovering the plant height,root length,and above-ground and below-ground dry weights to normal levels.In conclusion,low Mn conditions can induce akagare disease symptoms in low-cadmium rice varieties,and the treatment with foliar application of Mn fertilizer at 30 000 µmol/L can significantly alleviate akagare disease symptoms.